This application is based on and incorporates herein by reference Japanese Patent Application Nos. 2000-195504 filed on Jun. 29, 2000, and 2001-4890 filed on Jan. 12, 2001.
1. Field of the Invention
The present invention relates to a fluid controlling electromagnetic valve for adjusting the flow rate of control fluid, suitable for use in a vehicle.
2. Description of Related Art
In most of the fluid controlling electromagnetic valves of the prior art disclosed in JP-A-9-170675, the following assembly method is used when the individual components of the fluid controlling electromagnetic valve is to be assembled. A magnetic circuit is constructed by arranging a magnetic plate made of a magnetic material in advance resin mold integrally with a coil bobbin, and by crimping one end of a stator core made of magnetic material to the inner circumference of a yoke of a magnetic material. These components are held and fixed by resin-molding integrally with a housing.
However, in the fluid controlling electromagnetic valve of the prior art, the magnetic plate is resin-molded in advance integrally with the coil bobbin. Therefore, a molding resin having a predetermined thickness exists in a side gap portion, as formed between the magnetic plate and a moving core. As a result, the radial distance between the magnetic plate and the moving core is elongated to cause a problem that the magnetic efficiency and the responsibility drop.
Further, in the fluid controlling electromagnetic valve of the prior art, the stator core is fitted in the inner circumference of the coil bobbin. The stator core has the leading end portion, with which a piece of a nonmagnetic material is assembled for regulating the axial moving distance of the valve member. Thus, it is impossible to arrange the moving core close to the axial center of the coil. As a result, it is impossible to attain the overlapping portion between the coil and one axial portion of the moving core. Therefore, the axial size of the fluid controlling electromagnetic valve itself is enlarged to cause a disadvantage that the axial structure of the electromagnetic valve is large-sized.
In a conventional electromagnetic valve device for opening/closing the fluid passage, a magnetic circuit includes a moving core, a stator core facing the moving core in the reciprocating directions of the moving core, and a core plate arranged around the outer circumference of the moving core. The moving core is attracted toward the stator core by energizing a coil. By turning ON/OFF the coil, the valve member forming a moving member together with the moving core leaves and is seated on a valve seat to open/close the fluid passage.
Further, a resin film is made of resin material for insert-molding the stator core and the core plate. The resin film is coated on the inner circumference of the core plate, thereby guiding the outer circumference wall of the moving core reciprocally.
A first object of the present invention is to provide an electromagnetic valve capable of improving the magnetic efficiency and the responsibility.
A second object of the present invention is to provide an electromagnetic valve capable of reducing an axial structure thereof.
A third object of the present invention is to provide an electromagnetic valve device preventing a dispersion of fluid flow rate when the fluid flow rate is low, and which can be small-sized.
According to a first aspect of the present invention, an outer circumference of a moving core and an inner circumference of a magnetic member are arranged close to each other without any molding resin in a radial side gap which is formed between the outer circumference of the moving core facing one axial end face of a stator core and the inner circumference of a magnetic member through an axial air gap. Therefore, it is possible to improve the magnetic efficiency and the responsibility.
According to a second aspect of the present invention, there is provided an electromagnetic valve device in which a guide member arranged at a first stator core at the side facing a moving core and made of a nonmagnetic material guides an inner circumference wall of the moving core reciprocally. Therefore, it is unnecessary to prepare any additional nonmagnetic guide member between a second stator core arranged at the outer circumference of the moving core and the outer circumference wall of the moving core. The gap to be radially formed between the moving core and the second stator core is minimized to increase the magnetic attraction force for attracting the moving core to the first stator core. Thus, it is possible to reduce the number of turns of the coil, thereby reducing the size of the electromagnetic valve.
Where the number of coil turns is not reduced, on the other hand, the magnetic attraction force to attract the moving core increases. Therefore, it is possible to enlarge both the maximum gap between the first stator core and the moving core when the coil is deenergized and the minimum gap between the first stator core and the moving core when a moving member collides against a stopper. Therefore, the minimum gap is located at the position where the magnetic attraction force to attract the moving core axially is not excessively high. Thus, it is possible to lower the velocity for the moving core to collide against the stopper, thereby to reducing the bound of the moving core from the stopper. As a result, the dispersion of the fluid flow rate is reduced even when the valve opening time is so short that the fluid flow rate is low. Further when the bound of the moving core is reduced, it is possible to prevent the reduction of the opening area of the passage. Even at a low fluid flow rate, it is possible to retain a linear relation between the valve opening time and the fluid flow rate.